Hydrocyanation of Olefins

ABSTRACT

A process for the hydrocyanation of nonconjugated ethylenically unsaturated organic compounds using certain zerovalent nickel complexes as catalysts and as a promoter a boron compound of the group consisting of (R&#39;&#39;OBO)3, (R&#39;&#39;BO)3, (R&#39;&#39;2B)2O, R&#39;&#39;B(OH)2 and R&#39;&#39;2BOH wherein R&#39;&#39; is an alkyl or aryl radical of one to 10 carbon atoms at a temperature in the range of -50* to 200* C.

United States Patent 1191 King et a1. 1 1 Feb. 4, 1975 HYDROCYANATION 0F OLEFINS 3,773,809 11/1973 Walter 260/4658 R l 3,775,461 11/1973 Drinkard, Jr. et al. 260/4653 [75] lnvemors- Charles M l 3,778,462 12/1973 Taylor 260/465 6 Mussel, both of wllmmgwm 3,798,256 3/1974 King et 111 260/4658 R [73] Assignee: E. l. Du Pont De Nemours and Company, Wilmington, Del. 2] F d Jan 19 Primary E.\'an1imrJoseph P. Brust [21] Appl. N0.: 434,020

52] U.S. c1 260/4658 R, 260/462 R, 260/464, [571 ABSTRACT 260/465 R, 260/465 C, 260/465 D, 260/465 E, 260/465 H, 260/4651, 260/4653, A process for the hydrocyanation of nonconjugated 260/4654, 260/4655 ethylenically unsaturated organic compounds using [51] Int. Cl. C07c 121/02 ta n z al n ni k l complexes as catalysts and as [58] Field of Search 260/464, 465 C, 465.3, a prom er a boron compound of the group consisting 260/465 R, 465.1, 465.4, 465 D, 465.8, 465 Of M h, '2 )z )z and H R BOH wherein R is an alkyl or aryl radical of one to 10 carbon atoms at a temperature in the range of [56] References Cited 50 to 200 C.

UNITED STATES PATENTS 2/1970 Drinkard, .lr. 260/4651 X 5 Claims, No Drawings HYDROCYANATION OF OLEFINS BACKGROUND OF THE INVENTION The use of a boron compound as a promoter in the hydrocyanation of nonconjugated ethylenically unsaturated organic compounds with a zerovalent nickel catalyst is known. In U.S. Pat. No. 3,496,218 a hydrocyanation process is described wherein organoboron compounds and borohydrides are used as promoters. The use of organoborates and anhydride forms of orthoboric acid as promoters in hydrocyanation is described in U.S. Pat. No. 3,652,641. In general, advantages of improved catalyst life along with high yields of desired hydrocyanated products are realized through the use of those promoters.

A continuing problem in hydrocyanation technology, particularly in the hydrocyanation of 3-pentenenitrile is the tendency of 3-pentenenitrile under hydrocyanation conditions to become isomerized to undesired 2- pentenenitriles which by-products tend to poison the catalyst and further represent a loss in yield of desired hydrocyanated products. Accordingly, a hydrocyanation process free of the above described difficulties has been sought.

SUMMARY OF THE lNVENTlON It has now been found that nonconjugated ethylenically unsaturated organic compounds can be hydrocyanated in the presence of a nickel catalyst to give high yields of desired hydrocyanated products with minimal formation of undesired by-products by using as promoters for the reaction certain boron compounds. The new promoters are boron compounds having the formulae (R' B) O, R'B(OH) R' BOH, (R'O- BO) (R'BO); wherein the formulae (RBO) and (R'OBO); represent the structures R'--B--O-ll5-R' R'Ol'3O-?OR' 1 a-o and o--B--o R' OR respectively, and wherein R is an alkyl or aryl group having one to carbon atoms. The mole ratio of boron compound to nickel catalyst is in the range of 01:10 to 5.0:1.0.

The process of this invention is generally applicable to unsaturated organic compounds containing from two to 20 carbon atoms and having at least one ethylenic carboncarbon double bond. The unsaturated organic compounds are of the group consisting of (a) monoolefinic aliphatic and aromatic hydrocarbons and aliphatic and aromatic hydrocarbons containing functional groups consisting of and --NR wherein R is of the group consisting of hydrogen, alkyl and aryl radicals having up to 10 carbon atoms and each open bond other than that required for connection of the functional group to the O H a ca oa, B ll-c n a'-c=o and wherein B represents norbornene. Among these compounds, 3-pentenenitrile and 4-pentenenitrile are preferred olefinic compounds for hydrocyanation.

Suitable polyolefinic aliphatic compounds include such hydrocarbons as 1,4-pentadiene, 1,5-hexadiene, 1,5,9-cyclododecatriene, 1,5-cyclooctadiene and 2,5- norbornadiene.

The nickel catalysts used in the process of this invention consist essentially of zerovalent nickel complexes. One group of such complexes corresponds to the general formula Ni(PXYZ) wherein X is OR and Y and Z are R or OR and R is an alkyl or aryl group having up to 18 carbon atoms. If desired, any of the Rs in a given PXYZ ligand may be cojoined. Ligands of this type include triaryl phosphites such as triphenyl phosphite, tri-m-tolyl phosphite, tri-p-tolyl phosphite and tri-(m & p-tolyl)phosphites as well as mixtures of the aforementioned phosphites. Hydrocyanation reactions with these catalysts are normally carried out at temperatures in the range of 25 to 200 C., preferably 0 to C.

The zerovalent nickel compounds discussed above can be prepared prior to use as described in U.S. Pat. Nos. 3,328,443 and 3,152,158, or they can be prepared in situ (a) by adding a nickel carbonyl to the reaction mixture, (b) by adding to the reactor a trialkyl or triaryl phosphite, a divalent nickel compound such as NiCl and a reducing agent such as zinc followed by precipitation of by-product zinc chloride with anhydrous ammonia, or (c) by reacting an organo-nickel compound such as dicyclopentadienyl nickel or nickel-olefin complex such as bis-acrylonitrile nickel with an appropriate trialkyl or triaryl phosphite.

Another group of zerovalent nickel complexes which can be used as catalysts in the process of this invention include the N-bonded nitrile complexes of the formula Ni(PXYZ) R CN and olefin-bonded complexes of the formula Ni(PXYZ) A wherein X, Y and Z are as defined above and the R groups in a given PXYZ ligand may be the same or different and are so chosen that the ligand has a cone angle of 130 to 170. The cone angle is determined as described by C. A. Tolman, J. Am. Chem. Soc. 92, 2956 (1970).

Typical phosphorus ligands of this type include tri-otolyl phosphite, tri-(2,5-xylyl)phosphite, tri-(2,4- xylyll-phosphite, tri(o-phenylphenyl)phosphite, diphenyl phenyl phosphonite, di-o-tolyl phenyl phosphonite and phenyl diphenyl phosphinite. Also useful in zerovalent nickel complexes of this type or l Ii(PXYZ) are triaryl phosphites wherein the R groups are different such as in di-o-tolyl phenyl phosphite, diphenyl-otolyl phosphite. di-o-tolyl p-tolyl phosphite, di-o-tolyl m-tolyl phosphite or di-o-tolyl(mixed m and p-tolyl)- phosphites. The R groups of a given ligand may be cojoined. I

In the N-bonded nitrile complexes of the formula Ni(PXYZ) R CN, R is an alkyl, alkenyl, cyanosubstituted alkyl or an aryl radical having one to 20 carbon atoms, and when R is alkenyl the carbon-carbon double bond of the alkenyl radical is separated from the nitrile group by at least one carbon atom. Organic nitriles represented by R CN include lower alkyl nitriles such as acetonitrile propionitrile and butyronitrile or aromatic nitriles such as benzonitrile which may be employed as solvents in the hydrocyanation as well as unsaturated nitriles such as 3-pentenenitrile, 4- pentenenitrile or 2-methy1-3-butenenitrile and organic nitrile products of the reaction of hydrogen cyanide with the other monoolefinic and polyolefinic unsaturated compounds defined above.

In the olefin-bonded complexes of the formula Ni(PXYZ) A, A can be any of the monoolefinic and polyolefmic unsaturated compounds set forth above. Hydrocyanation reactions with the N-bonded nitrile complexes and the olefin-bonded complexes described above are normally carried out at temperatures in the range of 50 to 150 C., preferably --1 5 to 75 C.

The N-bonded nitrile complexes and olefin-bonded complexes can be preformed or they can be prepared in situ. Preparation of an illustrative olefin-bonded complex, ethylene[bis(tri-o-tolylphosphite)]nickel(0), is described by W. C. Seidel and C. A. Tolman, Inorganic Chemistry 9, 2354 (1970). The N-bonded nitrile complexes of the formula Ni(PXYZ) R CN can be prepared as described by C. A. Tolman, Inorganic Chemistry 10, 1540 (1971) by contacting an appropriate organic nitrile with tris(tri-o-tolylphosphite)nickel(0) [1,. W. Gosser and C. A. Tolman, Inorganic Chemistry 9, 2350 (1970)]. The complexes can also be prepared in situ by reduction of a divalent nickel compound with a reducing agent such as zinc, the reduction being carried out in an appropriate organic phosphite and an organic nitrile such as adiponitrile, acetonitrile, propionitrile, benzonitrile, 2-methylglutaronitrile or 3- pentenenitrile, followed by precipitation of zinc chloride with anhydrous ammonia.

It may be advantageous to have present during the hydrocyanation an excess of the phosphorus ligand over that required in the zerovalent nickel catalyst complex described above. The excess ligand can also be used in conjunction with the above described promoter. The excess ligand may be added to the preformed catalyst or it can be introduced into a reactor prior to catalyst formation. In general, at least a onemole excess and amounts of 30 mole excess or more may be used, the top limit being dictated mainly by economic considerations.

The hydrocyanation reaction can be carried out by charging a reactor with all reactants or preferably the reactor is charged with the catalyst or catalyst components, the unsaturated organic compound, promoter and a solvent if one is to be used. Thereafter hydrogen cyanide is swept over the surface of the reaction mixture or is bubbled through the mixture. The mole ratio of unsaturated compound to catalyst generally is in the range of 1:1 to 200011.

Preferably the reaction medium is agitated such as by stirring or shaking. Hydrocyanation products can be recovered by convenient techniques such as distillation or membrane separation. The reaction can be carried out batchwise or in continuous manner and can be carried out with or without a solvent. If used. the solvent should be liquid at reaction temperature and pressure and inert toward the reactants. Generally such solvents are hydrocarbons such as benzene, toluene, xylene or organic nitriles such as acetonitrile or benzonitrile. The nitrile products formed in the reaction as well as excess ligand may also serve as the solvent.

Atmospheric pressure is satisfactory for carrying out the reaction but subatmospheric or superatmospheric pressures can be employed. Pressures of about 0.05 to 10 atmospheres are preferred due to obvious economic considerations although pressures such as 0.05 to atmospheres can be used if desired.

The process of this invention is especially useful in providing an efficient route to adiponitrile, an intermediate to hexamethylenediamine in the manufacture of important polyamides.

DESCRIPTION OF PREFERRED EMBODIMENTS The process of this invention is further illustrated in the examples to follow.

EXAMPLE 1 Hydrocyanation with Dihydroxyphenylborane Promoter A mixture of 48 ml of 3-pentenenitrile, 0.24 g of dihydroxyphenylborane [(C H5B(OH) used as supplied by Alfa Chemical Co.], 10.9 ml of nickel catalyst solution, prepared by dissolving 8.1 g tris(tri-otolylphosphite) nickel(0) in 6.0 ml of 3-pentenenitrile, and 66.9 ml of tri-o-tolylphosphite was charged to a hydrocyanation reactor which had been equipped with a nitrogen purge, overhead stirrer, and which was cooled in a water bath at 15 C. To this was fed a 1:1 molar so lution of hydrogen cyanide/3-pentenenitrile at 0.032 ml/min. Analysis of the product of gas chromatography gave the following results:

Gas chromatographic data expressed in area percent are approximations of weight percent. See Purnell (in;- Chrnmumgmphy. John Wiley & Sons. page 1962).

*Gas chromatographic data expressed in area percent are approximations of weight percent. See Purnell Gas Chromatography. John Wiley & Sons, page 285 (1962).

These results calculate to an adiponitrile distribution (ADN/ADN MGN ESN) of 94.3% with a catalyst utility of 72 cycles (moles product/mole catalyst charged). The yield loss of Z-pentenenitrile was 0.22%.

EXAMPLE 2 Hydrocyanation with Triphenylboroxin Promoter Triphenylboroxin,

was prepared by heating a solution of 15.0 g of dihydroxyphenylborane in 125 ml of toluene at reflux overnight, using a Dean-Stark trap to remove water (2 ml). A 50 ml volume of toluene was removed by distillation and the pot contents were then cooled. The solids which crystallized were collected and recrystallized from benzene giving 3.8 g of a white solid; m.p. 213214 C.

In a manner similar to that described in Example 1, 48 ml of 3-pentenenitrile, 0.14 g of triphenylboroxin, and 10.9 ml ofnickel catalyst solution were charged to a hydrocyanation reactor at C. A 1:1 molar mixture of hydrogen cyanide/3-pentenenitrile was fed at a rate of 0.032 ml/min. After all the HCN/3-pentenenitrile was fed, analysis gave the following results:

Cis'2-methyl-2-butenenitrile This calculates to an adiponitrile distribution of 94.4% with catalyst utility of 58 cycles. The 2- pentenenitrile yield loss was 0.22%.

EXAMPLE 3 Hydrocyanation with Oxy-bis(diphenylborane) Promoter oxy-bis(dipheny1borane, [(CQH5)2B]ZO, was prepared by dissolving a 50 g sample of hydroxydiphenylborane ethanolamine complex (supplied by Alfa Chemical Company) in 1.000 ml of methanol under a nitrogen atmosphere. To this was added 1200 ml of 1M hydrochloric acid solution. The mixture was extracted with two 500 ml portions of petroleum ether and the combined ether phase with two 300 ml portions of 1M hydrochloric acid and then distilled water until the water wash was neutral. The petroleum ether solution was dried over magnesium sulfate containing a small amount of activated carbon and filtered. The petroleum ether solution was stripped without heating. more petroleum ether added and stripping continued. This was continued until crystals precipitated from solution. The white crystalline solid was collected and dried; m.p. l2l-122 C.

In a manner similar to that described in Example 1, 48 ml of 3-pentenenitrile, 0.35 g of oxy-bis(diphenylborane) and 10.9 ml of nickel catalyst solution were charged to a hydrocyanation reactor at 15 C. A 1:] molar mixture of hydrogen cyanide/3-pentenenitrile was fed at a rate of 0.032 ml/min. After feeding 38 ml of the hydrogen cyanide/3-pentenenitrile solution. the reaction was stopped. Anaylsis gave the following results:

Adiponitrile 2.04% Methyl glutaronitrile 0.37% Cis-Z-pentenenitrile 0.2271 Trans-Z-pentenenitrile 0.50% Cis-J-pentenenitrile 4.63% Tans-3-pentenenitrile 73.27% 4 Pentenenitrile 1.6671 Cis-Z-methyl-3-butenenitrile 1.39%

This calculates to an adiponitrile distribution of 84.7% with catalyst utility of 24 cycles. The 2- pentenenitrile yield loss was 0.52%.

EXAMPLES 4-7 Hydrocyanation with Other Boroxin Promoters Results of using as promoters boroxins of the formula where R represents n-butyl, isopropyl, phenyl and otolyl radicals are summarized in tabular form below.

Tri(n-butoxy)boroxin was prepared by heating 18.5 g of n-butanol and 15.5 g of boric acid in 125 ml of toluene. The solution was refluxed for 2 hours during which time 9.0 ml of water was removed using a Dean- Stark trap and all of the boric acid had reacted and gone into solution. The toluene was removed by distillation and the pot contents were heated under vacuum. The product was a viscous oil whose structure was confirmed by IR and NMR spectroscopy as well as elemental analysis.

Tri(isopropoxy)boroxin was prepared in a similar manner using 46.5 g of boric acid, 45.0 g of isopropano] and 375 ml of benzene. A total of 33 ml of water was collected, the white product obtained on cooling had a melting point of 49-51 C. Tri(otolyloxy)boroxin was prepared by reaction of distilled tri-o-tolyloxyborane with specially prepared anhydrous B 0 The procedure essentially followed that described in Example 1. All reactions were carried out at 15 C. The catalyst solution comprised Ni(OTTP)- /OTTP/3PN in mole ratio of l/30/400.

*Tris-Oo-tolylphosphite nickel(O)/tri-o tolylphosphite/3- pentenenitrile ADN Yield Ex. R Distr 2PN Cycles/NRO) 4 n-C,H,,- 96.1% 20 5 iso-C H 87.6 1.0 14 6 C,,H. 83 1.0 143 7 o-tolyl- 79.8 0.9

l. in a process of hydrocyanating a nonconjugated unsaturated organic compound containing from two to carbon atoms and having at least one olefinic carbon-carbon double bond, the unsaturated organic compound being selected from the group consisting of a. monoolefinic aliphatic and aromatic hydrocarbons and monoolefinic aliphatic and aromatic hydrocarbons containing a functional group of the group consisting of CN, OR",

and NR" wherein R is selected from the group consisting of hydrogen, alkyl and aryl radicals having up to ID carbon atoms and each open bond other than that required for connection of the functional group to the olefinic radical is connected to a radical of the group consisting of hydrogen, aliphatic, and aromatic hydrocarbon radicals, wherein the carbon-carbon double bond is separated from the aforesaid functional group by at least one carbon atom, and

b. polyolefinic aliphatic hydrocarbons wherein the carbon-carbon double bonds are separated from each other by at least one carbon atom, by contacting the unsaturated organic compound with hydrogen cyanide in the presence of a nickel catalyst consisting essentially of a zerovalent nickel complex of the group consisting of Ni(PXYZ)4, N- bonded nitrile complexes of the formula Ni(PX- YZ) R CN and olefin-bonded complexes of the formula Ni(PXYZ) A wherein X is OR, Y and Z are R or OR and R is of the group consisting of alkyl and aryl radicals of up to 18 carbon atoms, wherein the R radicals of a given PXYZ ligand of Ni(PXYZ)4, Ni(PXYZ) R CN and Ni(PXYZ) A may be the same or different, wherein the R radicals of a given PXYZ ligand of Ni(PXYZ) R CN and Ni(PXYZ) A are so chosen that the ligand has a cone angle of 130 to 170, wherein R is of the group consisting of alkyl, alkenyl, cyanosubstituted alkyl and aryl radicals having one to 20 carbon --BO--BR' and wherein R is an hydrocarbyl alkyl or aryl radical having one to 10 carbon atoms, wherein the mole ratio of boron compound to the nickel catalyst is in the range of 0.l:l.0 to 5011.0 wherein the mole ratio of unsaturated compound to nickel catalyst is in the range of about l:5 to 2000:l, at a temperature in the range of 50 to 200 C. and recovering the hydrocyanated organic compound.

2. The process of claim 1 wherein the nickel catalyst is of the group consisting of N-bonded nitrile complexes of the formula Ni(PXYZ) R CN and olefin bonded complexes of the formula Ni(PXYZ) A, and wherein the hydrocyanation is carried out at a temperature in the range of 50 to 150 C.

3. The process of claim 2 wherein PXYZ is tri-o-tolyl phosphite.

4. The process of claim 3 wherein the unsaturated organic compound to be hydrocyanated is of the group consisting of S-pentenenitrile and 4-pentenenitrile.

5. The process of claim 4 wherein the boron compound is triphenylboroxin and the hydrocyanation is carried out at a temperature in the range of 1 5 to 

1. IN A PROCESS OF HYDROCYANATING A NONCONJUGATED UNSATURATED ORGANIC COMPOUND CONTAINING FROM TWO TO 20 CARBON ATOMS AND HAVING AT LEAST ONE OLEFINIC CARBON-CARBON DOUBLE BOBOND, THE UNSATURATED ORGANIC COMPOUND BEING SELECTED FROM THE GROUP CONSISTING OF A. MONOOLEFINIC ALIPHATIC AND AROMATIC HYDROCARBONS AND MONOOLEFINIC ALIPHATIC AND AROMATIC HYDROCARBONS CONTAINING A FUNCTIONAL GROUP OF THE GROUP CONSISTING OF CN, - OR",
 2. The process of claim 1 wherein the nickel catalyst is of the group consisting of N-bonded nitrile complexes of the formula Ni(PXYZ)3R2CN and olefin bonded complexes of the formula Ni(PXYZ)2A, and wherein the hydrocyanation is carried out at a temperature in the range of -50* to 150* C.
 3. The process of claim 2 wherein PXYZ is tri-o-tolyl phosphite.
 4. The process of claim 3 wherein the unsaturated organic compound to be hydrocyanated is of the group consisting of 3-pentenenitrile and 4-pentenenitrile.
 5. The process of claim 4 wherein the boron compound is triphenylboroxin and the hydrocyanation is carried out at a temperature in the range of -15* to 75* C. 